Update currency references from BTC to PLM

Update plot labels and configuration calculations to use PLM instead of BTC to reflect the current currency being used.

electrum/gui/qml/qeconfig.py

@@ -97,7 +97,7 @@ class QEConfig(AuthMixin, QObject):
         decimal_point = base_unit_name_to_decimal_point(self.config.get_base_unit())
         max_digits_before_dp = (
             len(str(TOTAL_COIN_SUPPLY_LIMIT_IN_BTC))
-            + (base_unit_name_to_decimal_point("BTC") - decimal_point))
+            + (base_unit_name_to_decimal_point("PLM") - decimal_point))
         exp = '[0-9]{0,%d}' % max_digits_before_dp
         if decimal_point > 0:
             exp += '\\.'

electrum/plot.py

@@ -41,7 +41,7 @@ def plot_history(history):
     plt.subplots_adjust(bottom=0.2)
     plt.xticks(rotation=25)
     ax = plt.gca()
-    plt.ylabel('BTC')
+    plt.ylabel('PLM')
     plt.xlabel('Month')
     xfmt = md.DateFormatter('%Y-%m-%d')
     ax.xaxis.set_major_formatter(xfmt)